Control means for motor-driven letoffs



Oct. 5, 1948. PALMER r 2,450,485

CONTROL MEANS FOR MOTOR DRIVEN LETOFFS Filed July 26, 1946 OOIIOO\OOOO.

INVENTORS ALBERT PALMER VICTOR f-T sEPA we ex. WM

AT T O R N E Y Patented a. 5, 1948 CONTROL MEANS FOR MOTOR-DRIVEN LETOFFS Albert Palmer and Victo Mass, assignors to Works, Worcester, Massachusetts r F. Sepavich, Worcester, Crompton & Knowles Loom Mass., a corporation of Application July 26, 1946, Serial No. 686,291

Claims. (01. 139ll10) This invention relates to improvements in loom l-etoif mechanisms and it is the general object of the invention to provide control means for a motor which effects turning of the warp beam.

In our copending application Serial No. 592,986

filed May 10, 1945, we have shown a motor driven letoif operated by electronic circuits which are under control of the warp tension in such manner that when the tension attains a given maximum the motor comes into action to turn the beam slightly to reduce the tension. This control of the motor exists during loom operation, but it is desirable to be able to turn the beam either backwardly or forwardly when the loom is stopped. It is accordingly an important object of our present invention to provide control means by which the letofi motor can be caused to turn either forwardly or backwardly during loom stoppage by means of switch mechanism under manual control of the weaver.

Under certain conditions it may also be desirable to be able to advance the warp at a faster rate than that provided for by the warp tension controlled contactor and in order to accomplish this result it is a further object of our invention to provide means by which said contact can be manually closed during loom operation. Likewise, it may be desirable at times to reverse the letofl motor during loom operation and it is a further object of our invention to provide for such reversal.

Our improved control is therefore seen to be effective to drive the warp beam either forwardly or backwardly either during loom operation or =loom' stoppage.

With these and other objects in view which will appear as the description proceeds, our invention resides in the combination and arrangement of parts hereinafter described and set forth.

In the accompanying drawings, wherein a convenient embodiment of our invention is set forth,

Fig. 1 is a diagrammatic view of the warp system of a loom controlled by our invention, and

Fig. 2 is a diagrammatic view of the electric circuits by which the aforesaid letoff motor is controlled.

Referring particularly to Fig. 1, the letofi beam I 0 supplies warp W which passes over the usual whip roll H and then forwardly through the harness frames l2 and reed l3 toward the breast beam H. The warp beam is under control of a motor M which drives a reduction unit l5 operatively connected to a gear l6 turning with the beam. The unit I5 is a speed reducer and permits the use of a cheap and eflicient motor.

A contactor mechanism H has a foot it! which presses down against the warp but is raised bythe warp as the'tension of the latter increases, and when a given maximum warp tension is attained a contact within the mechanism H is closed to electrically connect two wires 49 and 20. The movable contact is not shown in Fig. 1,

Y but is indicated at 2| in Fig. 2, while the stationary contact is indicated at '22 and will be also located in the mechanism [1.

When the motor M turns in a forward direction the beam will be turned in a clockwise direction as view in Fig. 1 to supply warp for the weaving process and also relieve tension in the warp. After the tension has been temporarily relieved the motor comes to rest until the maximumtension is again attained. The details of the structural connections between the motor and the beam do not form a part of the present invention and these details may if desired be similar to those set forth in our aforesaid copending application. It is thought sufficient for present purposes to state that when the motor M moves in aforward direction beam ID will be turned to deliver warp, and when the motor is reversed the beam will be turned backwardly to increase warp tension or change the position of the fell 23 of the cloth 24 being woven. Such a reversal may be necessary after a pickout operation.

The motor is controlled by the-circuits shown in Fig. 2.' These circuits include two gas filled or power electronic tubes 30 and 3|, the former having a plate 32, a. grid 33 and a cathode 34, and tube 3| having a plate 35, a grid 36 and a cathode 31. Alternating current is supplied by wires 40 and 4| which are connected to primary 42 of a transformer T. The latter has a. secondary 43 provided with a center tap 44 and has upper and lower windings 45 and 46, respectively.

The motor is preferably of the direct current shunt wound type and includes an armature 50 and a field 5|. The armature circuit is under control of shipper handle 52 by means of a switch 53. When the loom is running the shipper handle is in the running position and closes switch 53, and under these conditions current will flow through the armature whenever the grids 33 and 36 are in a permissive condition and enable current to pass through their respective tubes. v

Thus, on one alternation when plate 32 is positive, the following circuit tends to energize the armature and will do so when grid 33 permits current to flow through tube 30: center tap ll, winding 45, wire 55, plate 32, through the tube, cathode 34, wires 56, 31 and 58, switch 53, wires latter part only of the electric alternations.

II and I0, armature IO, and wire II back to the center tap. On the next alternation plate II is positive and current tends to now in the following circuit: center tap l4. winding i, wire 02, plate 3!, through the tube, cathode 81, wire l1, and thence through switch It and the armature as previously traced back to the center tap. The motor armature will therefore be supplied with pulsating unidirectional current whenever current can pass through the tubes it and 3 I'.

The grids 22 and 2! are under control or a grid circuit the condition of which is altered by closure of the contacts'within oontactor mechanism II. The grid circuit includes the secondary I of a transformer T having a center tap l dividing the secondary into upper and lower windlugs 61 and 68, respectively. The primary 8! of transformer T is supplied with alternating current by wires I0 and II which may be connected to the wires and ti. Wire I0 contains a resistance R which together with the inductance of the primary 88 changes thephase of the latter with respect to the phase of the alternating current in wires 40 and 4|. The secondary ll is therefore out of phase with the secondary 42. Winding 61 is connected through protective resistance R to grid 23 by wire I2, and in similar manner the lower winding 88 is connected through resistance R2 to grid 38 by wire II. The grids are therefore out or phase with the plates and cathodes of their corresponding tubes.

The grid control circuits are connected to a source of direct current supplied by wires 15 and 18. These wires are bridged by a resistance R3 having an adjustable contact 11 which divides resistance R3 into upper and lower parts RU and RL.

When contact 2I is out of engagement with contact 22 the following direct current circuit is closed. Wire I5, resistance Rt, wires til and ti,

V the latter being connected to center tap 68,

condenser 82, wires 82 and '4, adjustable contact I1, and resistance RL to wire 16. This circuit imposes a constant direct current bias on the center tap 88 at a voltage which is determined by the values of resistances R4 and RL.

This imposed or impressed direct current voltage depresses the voltage of the windings 81 and 68 so that the zero level of the fluctuating voltage of the grids is below the zero level of the cathodes.

If it is desired to operate the motor at two different speeds, as set forth in the aforesaid copending application, the contact I1 will be set so that the difierence between the zero levels of the potentials of the grids and cathodes will be such that the potential of the grids will rise to the firing potential o.the tubes during the It should be understood, however, that the contact 'II can he so set that when contacts 2i and 22 are separated the armature ill will receive practically no current or an insufllcient amount to cause turning thereof, in which case the motor is idle for all practical purposes.

The conditions just described with respect to the grid circuit will exist when warp tension is below a. given maximum, whether the motor be idle or turning very slowly. When the warp tension attains the given maximum contact 2I will be moved into engagement with contact 22, whereupon the following circuit will be placed in electric parallel with resistance RL: wire II connected at junction 85 to wire 20, contacts 2| and 22, wire 20, resistance R5, and wire it. Closure of this circuit aflords an additional path for the iiow 0! current rrom junction It to wire ll resulting in a change in the potential of lunction II, which reduces the depressive effect oi. the direct current on the voltages of the windings 01 and it, whereupon the grids a and 28 rise in potential and produce a change in the tubes the effect of which is to increase motor speed, or start operation of the motor, depending upon the setting or contact TI. This change will persist so long as contact 2I engages contact 22, but with the reduction in warp tension incident to turning of warp beam I0 contact 2I will eventually move away from contact 22 and the grid circuit will be changed irom its permissive condition back to its preventive condition.

Much of the matter thus far described is set forth in the aforesaid copending application and is not specifically claimed herein, but is set forth in sufllcient detail to indicate how the circuits operate.

Our present invention is concerned more particularly with manual controlled switch means for the motor. The field switch FS has two blades 00 and BI permanently connected to wires '2 and 92 leading to the field 5|. Switch F8 has three binding posts 04, 95 and 86 the first and third of which are connected by wire 81 to the direct current source wire 16, and the intermediate post 85 of which is connected by wire 08 to the other direct current source wire It.

When switch F8 is to the left, or in the normal position shown in Fig. 2, current will flow through field II in such a direction as to cause forward turning of the armature, but when switch FS is thrown to its other or reverse position current through the field is reversed and the armature turns in a reverse direction.

A- second hand switch I00 independent 0! switch FS has blades IOI and I02 and is for the purpose of closing the armature circuit when the shipper handle 52 is in the of! position, and also for the purpose of shortcircuiting contacts 2I and 22. Switch I" is capable of assuming three positions and will ordinarily be in the normal open position in full lines shown in Fig. 2. When moved to the right to its first operative position, dotted lines, blade IIII will still be idle, but blade I02 will electrically engage elongated contact post I05 and switch 52 will be bridged by wire Iln connected to wire 60, blade I02, post I05 and wire III connected to wire 51. Movement of switch I" to its first operative, or intermediate position, will therefore establish the circuit through the armature even though the shipper handle be in non-running position. If contact I1 is set for continuous slow rimning of the motor the latter will turn when blade I02 engages contact I", otherwise the motor will be idle.

When switch I00 is moved to the extreme right to its second operative position shown in dot and dash lines, blade I02 will remain in engagement with contact I, but in addition, contacts 2I and 22 will be bridged by wires H2 and H3, and

circuit during loom operation and the motor can be caused to turn to cause additional advance movement of the warp beam if this condition is desirable in the weavers judgment.

From the foregoing it will be seen that we have provided means by which the motor of a motor driven letoif can be manually controlled to run either forwardly or backwardly either during loom operation or loom stoppage. Switch I00 when thrown to its extreme temporary position has the effect of altering the potential of the grids in such manner as to affect turning of the motor, either to start it or increase its speed, but the direction of turning is under control of switch F The switches FS and I00 will normally tend to remain in the full line positions shown in Fig.

2 to cause forward running of the motor and permit control of the contacts 2| and 22 by warp tension only.

Having thus described our invention it will be seen that changes and modifications may be made therein by those skilled in the art withoutdeparting from the spirit and scope of the invention and we do not wish to be limited to the details herein disclosed, but what we claim is:

1. In letoff mechanism for a loom having a warp beam operatively connected to a motor which when running effects turning of the beam,

causing the latter to run at two different rates of speed, and manual control means for the electric circuit means normally in inoperative position relatively to said electric circuit means but movable to two different operative positions in one of which said electric circuit means is caused to turn the motor at one of said speeds thereof, and said manual means when in the other operative position thereof causing the electric circuit meansto effect running of the motor at the other speed thereof.

2. In letoff mechanism for a loom having a warp beam operatively connected to a motor which when running effects turning of the beam, electronic circuit means including an electronic tube having a grid, said electric circuit means normally tending to cause running of the motor,

electric circuit means for the motor capable of control means for the grid effective when the warp tension is less than a given maximum to enable the grid to prevent the electric circuit means from causing running of the motor but operative when the tension of the warp attains said given maximum to alter the grid in such manner as to enable the electric circuit means to cause running of the motor, and manual switch means connected to said controlmeans for the grid and effective when the warp tension is less than said given maximum to alter the grid to sion attains a given maximum to cause running of the motor, means to render said electric circuit means inoperative when the loom stops, and normally open manual switch means closable during loom stoppage to restore the electric cir-,

cuit means to operative condition.

4. In letoff mechanism for a loom having a warp beam operatively connected to a motor which when running effects turning of the beam, electric circuit means including a switch normally effective when the latter is closed and the warp tension attains a given maximum to cause running of the motor, loom shipper mechanism maintaining said switch closed during loom operation, said switch opening during loom stoppage to render said electric circuit means ineffective to cause running of the motor, and normally open manual swicth means connected in parallel with the first named switch and effective when closed during lcom' stoppage to cause said electric cir cuit means to effect running of the motor, pro- 5. In lctoff mechanism for a loom having a warp beam operatively connected to a 'motor which when running effects turning of the beam, operating electric circuit means for the motor, a control circuit means for the operating electric circuit means which when in one condition causes the perating electric circuit means to effect running of the motor and when in another condition prevents said operating electric circuit means from causing running of the motor, said operating electric circuit means normally being inoperative during loom stoppage, and normally open manual switch means effective when closed during loom stoppage to cause said control circuit means to be in said one condition thereof to cause said operating electric circuit means to effect running of the motor.

ALBERT PALMER. VICTOR F. SEPAVICH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

